This invention relates to decorative fastener assemblies and more particularly to a decorative fastener assembly of the type including a nut insert and a decorative cap fitted over the nut insert.
Decorative fastener assemblies of the nut insert and decorative cap type are in common usage especially in the automotive industry wherein they are used for holding a wheel on a motor vehicle while presenting an attractive decorative appearance. When using a decorative cap fitted over a nut insert, it is always necessary to insure that the decorative cap is not dislodged from the nut insert and to insure that contaminants do not enter into the space between the nut insert and the decorative cap. Welding, adhesives, and crimping have been utilized to secure the decorative cap to the nut insert and O-ring seals have been utilized to preclude the entry of contaminants into the space between the decorative cap and the nut insert. Each of the described securement techniques has disadvantages. The welding technique creates a corrosive site between the nut insert and the cap which when attacked by moisture may ultimately lead to weakening or failure of the bond. The relatively low tensile and shear strengths of the adhesive bond present a problem as well as difficulties encountered in masking the nut threads from adhesive during the adhesive application process. The crimping technique allows some movement of the cap when it is wrenched on the nut. Whereas the O-ring seal is effective in precluding the entry of moisture between the cap and the nut insert, the seal itself has no securement function.
This invention is directed to the provision of an improved decorative fastener assembly.
More specifically, this invention is directed to a decorative fastener assembly which may be inexpensively produced, in which the bond between the cap and the nut insert is effective even over sustained periods of use, and in which the entry of moisture between the cap and the insert is precluded.
The decorative fastener assembly of the invention is the type including a nut insert and a decorative cap, the nut insert including a flatted portion proximate a top end of the nut insert for wrenching, a load bearing portion proximate a bottom end of a nut insert, an external annular ridge intermediate the flatted portion and the load bearing portion, and a central bore including internal thread means for threadably engaging a bolt; the decorative cap including a flatted portion fitted over the flatted portion of the nut insert, a top end wall portion fitted over the top end of the nut insert, and a flange portion at an open bottom end of the cap proximate the external ridge of the nut insert.
According to one aspect of the invention, the cap is welded to the nut insert, and the flange portion is crimped around an outer cylindrical surface of the ridge and under a lower annular surface of the ridge. This arrangement allows the crimped flange to assist the weld in precluding dislodging of the cap from the nut insert.
According to a further feature of the invention, the fastener assembly further includes an O-ring seal positioned around the nut insert above the nut insert ridge between the cap flange the ridge. This arrangement allows the O-ring seal to function to preclude the upward entry of contaminants between the cap and the nut insert whereby to protect the integrity of the weld.
The invention further provides a method of fabricating a decorative fastener assembly. According to the invention methodology, a nut insert is formed including a flatted portion proximate a top end of the nut insert for wrenching, a load bearing portion proximate a bottom end of the nut insert, an external annular ridge intermediate the flatted portion and the load bearing portion, a central bore including internal thread means for threadably engaging a bolt, and a weld projection extending upwardly from the top end of the nut insert; a decorative cap is formed including a flatted portion sized for fitting over the flatted portion of the nut insert, a top end wall, and a flange portion at an open bottom end of the cap; the nut insert is inserted into the open bottom end of the cap to move the flatted portion of the nut insert into the flatted portion of the cap and seat the weld projection against the top end wall of the cap; the cap is welded to the nut insert at the interface of the top end wall of the cap and the weld projection while pressing the nut insert and cap together whereby to melt the weld projection and spread the material of the weld projection to diminish the overall height of the nut insert to allow the cap to move further downwardly on a nut insert; and the cap flange is crimped over the nut insert ridge. This methodology provides a simple and efficient means of manufacturing a decorative fastener assembly in which the cap is held to the nut insert both by welding and by crimping.
According to a further feature of the invention methodology, the methodology includes the further step of positioning an O-ring seal around the nut insert prior to inserting the nut insert into the open bottom end of the cap. In this arrangement, the O-ring seal is clamped between the nut insert ridge and the cap flange in response to insertion of a nut insert into the cap and the O-ring seal is further squeezed between the nut insert ridge and the cap flange in response to the further downward movement of the cap on the nut insert resulting from the welding of the cap to the nut insert.
Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.